The present invention relates to an insulated lunch box for storing hot and cold food so as to maintain the temperature of the stored food over extended periods of time.
Lunch boxes are used to store food for consumption after a period of time. Insulated lunch boxes are especially useful for storing food which must be kept hot or cold for improved taste and possibly to prevent spoilage. Generally, a lunch box is a container with a number of chambers, receptacles or trays for carrying different foods which are to be stored at different temperatures and/or which are to be eaten at different temperatures, some hot and some cold. It is also known to provide heating and cooling devices in parts of the lunch box for heating or cooling some of the stored foods for greater enjoyment.
A number of lunch boxes, are shown in, for example, U.S. Pat. Nos. 5,082,115; 5,052,369; 5,007,743; and 4,830,190. However, the lunch boxes disclosed in the prior art suffer from the problem that food which is to be kept either hot or cold inside the lunch box cannot be maintained at the appropriate temperature for four or more hours because air, which is trapped inside the lunch box, allows convection of heat to or from the stored food. Moreover, in the prior art lunch boxes, there usually is wide spread contact between the stored food and inner surfaces of the lunch box. Such contact can be direct or through a container in which the food is placed. This contact between hot or cold food stored inside the lunch box and inner surfaces of the lunch box facilitates transfer/conduction of heat to or from the food thereby making it more difficult to maintain the food at a desired temperature over an extended period of time. The food, therefore, loses taste and could even spoil. Therefore, there is a need for a lunch box which more effectively preserves food stored in it by maintaining the temperature of the food at an optimal temperature range over a period from early morning to lunch time.